World 5 (Super Mario World 2: Yoshi's Island)
From the Super Mario Wiki
World 5 is the fifth of six worlds in the game Super Mario World 2: Yoshi's Island and its remake Yoshi's Island: Super Mario Advance 3. It consists of ten levels two being castles, and two bonus stages. It takes place on both the tops of snowy peaks, and in the clouds that surround them.
 List of Levels